25 November 2012

We are always on the lookout for good headphone amplifiers and here is a great simple tube design that will work with a wide range of headphones. This tube headphone amplifier design comes to us from Bruce Heran. The tube headphone amplifier is designed along the lines of the Oddwatt power amplifiers with the
exception that this headamp does not require a driver stage. The headphone amplifier uses only one 6DJ8 tube per channel in a push-pull configuration. All the
circuit gain is in the single output stage. A constant current source (CCS) is used on the cathodes to force class-A operation. The headphone amplifier circuit has no coupling capacitors
and no feedback loops. There are a total of only 7 components
including the tube in each channel. The output stage is transformer coupled and the two transformer choices will accommodate most headphones with an impedance between 32 and 600 ohms.

6DJ8 (ECC88) Valve Headphone Amplifier - Inside

6DJ8 (ECC88) Tube Headphone Amplifier - Finished

The frequency response at the 50 mW level is from 20 Hz to 28 kHz within 0.5 dB and the wide band signal-to-noise is at -84 dB. Power consumption of the headphone amplifier is approximately 20 Watts (W). Bruce reports excellent results with his Koss Pro4AAT (250 ohms) and Sennheiser
HD-280 PRO (64 ohms) headphones. "there was no audible noise or hum and the response
was rich and clean" For full project details, see the DIY 6DJ8 (ECC88) Tube Hi-Fi Headphone Amplifier Project page.More DIY Headphone Amplifier Projects: